1. Field of the Invention
This invention relates to plastic pallets and in particular to plastic pallets developed to operate within radio frequency rich environments.
2. Description of the Related Art
Pallets are used to move products through supply chains and to store products between movements. Wood has been the preferred material of pallet construction. A number of standard pallet sizes, such as the Grocery Manufacturers Association (“GMA”) style 48×40 inch pallet, have been used to facilitate the wide spread use of wooden pallets across differing distribution networks with some success. Such pallets are utilized in great numbers in what is known in industry as “pallet exchange”. It is estimated that there are 2.2 billion wood pallets in North America.
Wooden pallets have problems. In particular, wooden pallets deteriorate with use and cause problems that add user costs. Fortune 500 companies that utilize large numbers of wooden pallets seek to overcome problems associated with deteriorating pallets by hiring wooden pallets from pallet rental companies. Pallet rental companies maintain large pools of wooden pallets and repair damaged wooden pallets before they are re-used. Large users of wooden pallets have therefore been able to manage their costs by transferring the burdens associated with wooden pallet deterioration and pallet exchange to other supply chain service companies.
Although the business model used by pallet rental companies has enjoyed some success, there have been problems. For example, it is difficult to keep track of wooden pallets after they are let for hire. Chep International, the largest pallet pooling company, reportedly lost 14 million wooden pallets, and booked a $238 million adjustment in its financial reporting. These pallet tracking and other inherent wooden pallet problems have increased the need to modify business models relating to the use of pallets for rental purposes.
For example, there are several business conditions and economic factors combined with a convergence of technologies that have led to the creation of track and trace technologies exemplified by the term RFID (radio frequency identification) RFID holds the promise of providing real time supply chain visibility so that in the first instance pallet rental companies would be able to track their rental assets and in the second instance so that pallet users could trace their product through the supply chain.
Implementation of RFID, in one respect, involves the attachment of a tag, which contains a unique identification code, onto a pallet and a distributed network of tag readers. The tag readers associate a tag with a known location to determine the status or progress of the pallet within the supply chain. In this manner, the pallet can be tracked and traced with some accuracy, and the status of the pallet can be queried and displayed according to well understood principles by industry.
Implementation of any RFID system is problematic with regard to wooden pallets. For instance, in U.S. patent application Ser. No. 10/701,745, which is assigned to Chep International, it is suggested that a tag can be positioned exteriorly upon a nine block GMA style 48×40 inch wooden pallet. Thus, as each tag is read its location would be known. There are however several problems with such an arrangement. In the first instance, it is known that wood absorbs liquid and liquids interfere with radio frequency signals. Therefore, the reliability of communication between the reader and the tag could be compromised by the wooden materials utilized in the construction of the pallet. In a second instance, a tag that is exteriorly positioned upon a surface of a wooden pallet would be subject to a high level of the wear and tear. The impact of a fork tine against an exteriorly positioned tag could result in the destruction of the tag and the loss of the data stored in the memory of the tag. In the final analysis, wood is not a suitable material for constructing pallets that must work within radio frequency rich environments.
As a result of some of the aforementioned circumstances and problems industry has attempted to utilize plastic materials in the construction of pallets. The replacement of wood with plastic has had some success but there have been problems associated with the use of plastic pallets that are to be used in association with track and trace technologies including RFID.
An early example of a plastic pallet that employees a data collection device (i.e. a tag) to provide a track and trace capability is described in U.S. Pat. No. 5,971,592 to Kralj et al. In this cited reference the data collection devices are contained in cavities located on each side of the four corners of the pallet. The apparent need for a tag in each corner is due to, the short interrogation range of the readers of the day. In this arrangement a plurality of tags are required which would be more costly than an arrangement in which only one tag is required.
Similarly, in U.S. Pat. No. 6,199,488 to Favaron et al., a plastic pallet with two RFID cards (i.e. tags) is shown and described. The cards are positioned at angles and in the opposite corners so that at least one card is in communication range with a detector (i.e. a reader) from a side position (i.e. from a portal column or fork lift mounted reader). Although the Favaron et al. arrangement utilizes fewer tags than the Kralj et al. arrangement, Favaron et al. nevertheless utilizes more than one tag which is less economical than the use of one tag. A similar arrangement, requiring two or more tags, is disclosed in more thorough detail in U.S. Pat. No. 6,669,089, which was filed Nov. 12, 2001, and is assigned to 3M Innovative Properties Company.
Presumably, the arrangements suggested by Kralj et al. would be more reliable than the arrangement of application '745 because the devices of Kralj et al. are enclosed within the structures forming the pallet and therefore are less susceptible than exteriorly mounted tags to damage from fork impacts, wear and tear and the like. Furthermore, Kralj et al. would be more reliable than Favaron et al. because although Favaron et al. contemplates the containment of the tag within the body of the pallet, the Favaron et al. arrangement could allow liquids and other debris to penetrate into and accumulate within a socket wherein the tag of Favaron et al. is located. Liquids and debris within the socket could damage the tag or result in unreliable communication between the tag and the reader.
In U.S. Pat. No. 6,483,434, which is assigned to IFCO Systems, another pallet rental company, it is suggested that the delicate components of a transponder (i.e. a tag) can be protectively housed inside a plastic casing. The casing containing the delicate transponder could be subsequently positioned inside an injection mold and incorporated safely into an injection molded component forming part of a plastic pallet. This arrangement would protect the tags and overcome the problem associated with Favaron et al, wherein the tags are indirectly exposed to wear and tear.
Although the arrangements encasing the RFID tags within the plastic pallet embodiments cited above offer levels of protection superior to the method of application '745, such arrangements nevertheless have additional problems. In particular, in order to remove, replace or repair the tags of the prior art references, the plastic pallets themselves would have to be deconstructed or destroyed to provide access to the tags. Accordingly, the prior art does not contemplate an efficient means to either replace defective or damaged tags or to upgrade long lasting plastic pallets with new tags incorporating enhanced capabilities as these become available. It should be noted that a plastic pallet can have a life span of +/− ten years, which length of time may easily exceed the lifecycle of a deployed RFID technology.
In U.S. Pat. No. 6,814,287 to Chang et al. a pallet apparatus equipped with a radio frequency recognition module is described. In a first wooden pallet embodiment the module comprises a molded cup forming a compartment that receives a tag. The cup is covered by a cap to enclose the tag inside the compartment. The module is inserted into a cavity formed in a block or stringer of the wooden pallet. In a second plastic pallet embodiment, the module comprises a removable clip for holding a tag and the clip attaches to the exterior of the plastic pallet. Both embodiments provide an efficient means for accessing a tag without deconstructing or destructing the pallet itself. However, in both cases the module could become detached from the associated pallet resulting in the loss of data and possibly the pallet.
In the above cited references two or more tags are suggested so that information can be obtained from at least one tag. However, in order to write information into the two or more tags, the tags would have to be synchronized with one another. This adds complexity to the implementation of RFID methods and systems. When only a single tag is attached to one side of a pallet, the pallet itself could become an obstacle. In this case the pallet would need to be rotated so that the pallet side with the tag faces the reader. Rotating the pallet is time consuming.
Accordingly, it has been suggested that a tag can be positioned substantially in the center region of the pallet. For example, publication document Netherlands 9401836 proposes locating a tag in the center of a pallet and mounting readers on the tines of a fork lift to enable the reader to communicate with the tag. This arrangement is not amenable to reading the tag from the side through a portal mounted reader. For example, the metal tines could block signals intended for the tag. In U.S. patent application Ser. No. 10/962,574, a preferred embodiment involves forming a through hole penetrating from one to the other side of the pallet, and positioning a tag inside the through hole in the vicinity of the middle of the pallet. The through hole is characterized as a transmission pathway for radio frequencies traveling between the tag and the reader. One problem with U.S. patent application Ser. No. 10/962,574 is that the through hole could collect debris that could impair the operability of the tag.
As discussed above, the life cycle of a plastic pallet may exceed the useful life cycle of a tag technology. Therefore, it would be advantageous in the adaptation of the plastic pallet to anticipate replacement of earlier tags with technologically up-dated tags. In U.S. Pat. No. 6,844,857, assigned to Linpac Moulding, it has been suggested that a recess, provided with a cover, could be developed to enable the removal and exchange of a circuit (i.e. tag IC) to program the circuit with current data or to exchange the circuit in the case of damage or malfunction or to update tag technology. Although the arrangement does not contemplate the destruction of the plastic pallet to access the tag IC, the recess of U.S. Pat. No. 6,844,857 is not developed to accommodate more than one tag IC at a time. This is a problem because there is a need to provide pallets with a plurality of tags so that the pallet can function across non-interoperable RFID systems existing within the supply chain.
In U.S. Pat. No. 6,816,076, assigned to Allibert Equipment, the advantage of providing a plastic pallet with a tag holder (i.e. a recess) is offered. The tag holder is an open design and provides an easy way to change a tag. The carrier (i.e. pallet) disclosed in U.S. Pat. No. 6,816,076 also contemplates the use of first and second tags involving a relay relationship, in which the antenna of the second tag is operable to increase the read range of the first tag. Such an arrangement is impractical because the first tag incorporated into the plastic pallet that contains the unique pallet ID becomes redundant once the unique ID of the first tag is associated with the unique ID of the second tag.
What is needed is a plastic pallet that is adapted to operate in a radio frequency rich environment. In particular, the pallet must be able to protect RF devices from wear and tear. Where practical, only one tag indicative of a first characteristic should be required, not two tags as is known in the art. The pallet must also provide access to the devices for any number of purposes as would be anticipated in the art.